Care of hospitalized patients by "hospitalists"- often defined as physicians who dedicate at least 25 percent of their practice to inpatient care- is a recent, growing, and controversial trend in health care delivery in the United States. But despite the growth of interest in hospitalists, there have been few scientific evaluations of the concept. The comprehensive aim of this proposed research is to measure and analyze the effects of hospitalists on quality of care, costs, and medical education on the general medicine services of six academic medical centers: Brigham and Women's Hospital (BWH), University of New Mexico (UNM), and the University of Wisconsin (UW). The comprehensive aim of this research will be pursued through three specific aims: Specific Aim number 1- To assess whether hospitalists affect the cost and quality of inpatient care. This will be accomplished by analyzing the outcomes of 32,8000 patients assigned to hospitalists or non- hospitalists over two years using a quasi-randomized design based on day of the week of admission. Quality of care will be measured by a set of disease-specific and cross-disease process of care measures, and a wide range of outcomes, including in-hospital and post-discharge mortality, readmission, emergency room use, functional status, and patient satisfaction. Specific Aim number 2- To assess the mechanisms by which hospitalists may affect the cost and quality of care. Understanding these mechanisms is essential if hospitalist programs are to be designed in ways that permit them to achieve their desired benefits. This will be accomplished by developing measures to test a variety of specific hypotheses concerning mechanisms by which hospitalists may have their effects and determining whether these measures are related to changes in costs and outcomes. Specific Aim number 3- To assess the effects of hospitalists on housestaff and medical student education and satisfaction. This will be accomplished by surveys administered to medical students and housestaff.